Pendant air bearing load supporting device



Jan. 26, 1965 H. A. MACKIE 3,1 7,

PENDANT AIR BEARING LOAD SUPPORTING DEVICE Filed Dec. 21, 1961 IN VEN TOR.

Z2 ATTORNEY United States Patent 3,167,145 PENDANT AIR BEARING LOAD SUPPQRTING DEVICE Harry A. Maclrie, Birmingham, Mich., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Dec. 21, 196i, Ser. No. 161,048 8 Claims. (Cl. 18tl-7) This invention relates to overhead conveyors and more particularly to overhead conveyors utilizing pendant air bearings as the load supporting medium.

An object of the invention is to provide an improved overhead conveyor system.

Another object is to provide an overhead conveyor in which the supported load is evenly distributed over a relatively large area of the surface support.

A further object is to provide a pendant air bearing construction especially adapted for overhead conveyors.

Still a further object is to provide an air bearing supporting device which is suspended from a ceiling or other horizontal structural surface by means of pressure differential induced at opposite sides of the air bearing.

Still another object is to provide a bearing of the type referred to which comprises a rigid annulus and a flexible annulus having their respective circumferential boundaries secured together to form an annular cavity of variable cross section, the flexible annulus being disposed so as to face a ceiling surface and the entire bearing being provided with air flow generating means disposed in relation thereto so that air is inducted into the space be tween the ceiling and flexible annulus and discharged downwardly through the rigid annulus, such air flow producing a continuous subatmospheric condition between the flexible annulus and ceiling so that the entire bearing is supported in frictionless relation with the ceiling by the pressure differential between atmospheric and subatmospheric pressure.

Still a further object is to provide a device of the type described wherein the rigid annulus includes venting means providing communication between the annular cavity and atmosphere so that during operation of the device the cavity is inflated by atmospheric pressure and causes the flexible annulus to distend upwardly to form a generally frusto-conical plenum cavity between the ceiling and the flexible diaphragm, the effective support area of the air bearing being defined by the area contained within a circle bounded by the uppermost distention of the flexible a11- nulus.

A yet further object is to provide a supporting device of the type described incorporating a motorized hoisting mechanism for elevating portable loads for horizontal movement while totally supported vertically by the bear- 1ng.'

Yet another object is to provide an arrangement of the stated character wherein the hoisting mechanism is mounted on the air bearing in substantial alignment with a vertical axis passing through the geometric center of the hearing so that any imbalance in the elevated load will not cause a corresponding imbalance in the rigid portion of the air bearing.

These and other objects, advantages and features of the invention willbecome more fully apparent as reference is had to the accompanying specification and drawing wherein: i

FIG. 1 is an elevational view, partly in section, of an air bearing supported hoisting mechanism and associated building structure in accordance with the invention; and

FIG. 2 is an enlarged sectional elevational view of a portion of the structure of FIG. 1 illustrating certain details of construction of the air bearing device.

ice

in the art and are employed in profusion in industry and commerce for various purposes. In general, such devices require the provision of rails or guideways which are secured to the building structure and in turn supported wheeled prime movers having cable or chain hoist mechanisms depending therefrom adapted to engage and lift loads for transportation to various points in the building within the liimits defined by the guideways. While such devices are exceedingly useful, rather elaborate installations are involved, and they are generally not suitable for buildings having totally surfaced ceilings, such as might be the case in stockrooms and warehouses for certain types of materials or finished product.

The present invention contemplates an economical, relatively uncomplicated, yet eflicient, conveyor hoist combination which i especially adapted for use in finished building structures. It is further ideally suited for use where it is desired to transport relatively great weights with a very moderate expenditure of power. To this latter end, the device is constructed so as to utilize the pressure of atmospheric air when supporting the loads involved.

As seen best in FIG. 1, there is shown a. conveyor and hoist structure wherein the reference numeral 2 designates generally a smooth fiat horizontal surface which in this case may be taken as the ceiling of a building structure, not shown. Located immediately vertically below ceiling 2 is an air bearing device 4 which is generally circular in plan form. Secured centrally on the rigid fiat lower surface 6 of bearing 4 is a depending framework 8 which has mounted therein an axial blower 10. During operation of blower 10, air is inducted from above the bearing and is exhausted downwardly so that the space 12 between the upper surface of the bearing and the lower surface of the ceiling is maintained in a subatmospheric condition which results in atmospheric pressure exerting an upward force which suspends the bearing adjacent the ceiling and in slightly upwardly spaced relation from the parking channels 13 and 14 secured to ceiling 2. It will be understood that the inturned flanges 16 and 18 of parking channels 13 and 14 serve to support the air hearing when the blower 10 is inoperative. To this end, the channels are located on the ceiling at some convenient remote point thereon. Furthermore, since the channels perform only the parking function,the length thereof need be only about equal to the diameter of the bearing. Mounted on the lower surface. of bracket 8 is a conventional electric motor driven reduction gear hoist mechanism 20 which includes cable structure 22 depending therefrom. At the lower end of cable structure 22 is a standard swivel hook 24' adapted for engagement with sling elements 26 and 28 of a platform or pallet 39 on which is borne a typical I industrial load.

at a point coinciding with an imaginary vertical axis pass- 1 vided by atmospheric pressure bearing upwardly against Overhead conveyors of various types are well known 1 ing through the geometric center of the bearing. Thus, even though the pallet 30 is capable of angular inclination with respect to hook 24, any maldistribution of load on the pallet is nevertheless applied to the hook in a line perpendicular thereto. Cable assembly 22 in turn trans- .mits the load to the pulley 32 of hoist 20 which is precisely centered with reference to the geometric centerof the bearing, with the result that the total load is evenly distributed with respect to the effective support area prothe undersurface of bearing 4. In this way, one of the more common shortcomings of air bearings is overcome; namely, the tendency to .spill and hence become inoperative in the presence of any significant load imbalance.

In accordance with the principal feature of the invention, the air bearing 4 is constructed and arranged in a manner which imparts functional efficiency heretofore unobtained in conventional pressure differential supported structures. is formed of a lower rigid annular platform 6 having one or more apertures 7 formed therein and an upper imperforate flexible annular diaphragm 34. The outer periphery 3.6 of diaphragm 34 overlaps the outer boundary 38 of platform 6 and is secured to the underside of the latter by a sealing ring 40. The inner boundary 42 of diaphragm 34 in turn is clamped to the upper surface of platform 6 by an annular clamping ring 4-1 which bounds the central opening 46 formed in platform 6. As stated previously, the framework 8 and axial blower 10 are located in alignment with opening 46 in platform 6. Therefore, during operation of the blower, air flow follows the direction indicated by the arrows and due to the proximity of the platform to the ceiling 2 tends to create a subatmospheric pressure in the space 12. This subatmospheric pressure tends to lift the diaphragm 34 upwardly away from platform 6, which movement is permitted by the entrance of atmospheric air into the annular cavity 48 through vent apertures '7. As soon as the diaphragm has assumed the general cross-sectional configuration shown in FIG. 2, the space 12 expands to include a generally frusto-conical cavity 59, the base area of which is defined by a circle bounded by the uppermost distended portion 52 of diaphragm 34. The gap 54 between ceiling 2 and the circle defined by distended portion. 52, while greatly exaggerated for the sake of clarity, is in reality of from two to four thousandths of an inch, which gap while extremely small is nevertheless suflicient to eliminate frictional contact between the bearing and the ceiling while effectively maintaining the pressure differential between the cavity 50- and atmospheric pressure on the lower surface of the hearing.

In practice, it has been found that the diameter 56 of maximum distention 50 varies in accordance with the load imposed on the bearing. Of special significance is the fact that the diameter 56 and hence the support area increases as the load increases with the result that a greater effective area of load support occurs as the load is increased. In addition, should any outside influence cause the rigid portion 6 of the bearing to incline from its normal horizontal position, the diaphragm 34- tends to distend asyrnetrically to maintain conformance of diaphagram 34 with the ceiling 2 and thereby maintain the uniformity of shallow gap 54 which accounts for the extraordinary operational efficiency of the device. Further, the atmospheric pressure exerted within cavity 48 on diaphragm 34 permits easy adaptation of the latter to moderate irregularities of the surface or ceiling 2. By. increasing the depth of convolution of diaphragm 34, the air bearing is capable of maintaining maximum operating efiiciency over ceiling irregularities which would render conventional air bearings totally inoperative.

From the foregoing it will be seen that a novel and inexpensive overhead conveyor structure has been provided. It is to be particularly noted that extraordinary load supporting capability may be derived from relatively small expenditure of power. By way of example, reduction of pressure within plenum 50 to 7 pounds per square inch by operation of blower 10, produces a theoretical maximum lift effect wherein for each square foot of area within the diameter 56, a load in excess of 1 thousand pounds may be supported. In addition, the load imposed on the ceiling is evenly distributed over the corresponding area and therefore avoids stresses which accompany localized loading such as occur in conventional conveyor structures. This is to say that in the case just described, the stress on the ceiling structure amounts to slightly less than 7 pounds per square inch, which is well within the capabilities of rather ordinary building structures. It is also to be noted that although in the embodiment shown, means are provided for supporting the bearing adjacent to the ceiling To this end, as shown in FIG. 2, bearing 4 4 when the bearing blower is inoperative, a conveyor system incorporating the invention is in no sense limited to operation confined to predetermined paths dictated by rails but is free to operate omnidirectionally over an entire ceiling surface, the two retainer rails being utilized only when the bearing is in an inoperative parking position.

While but one embodiment of the invention has been shown and described, it will be apparent that other changes and modifications may be made therein. It is, therefore, to be understood that it is not intended to limit the invention to the embodiment shown, but only by the scope of the claims which follow.

I claim:

1. A surface proximate air bearing comprising a rigid annulus and a flexible annulus having their respective circumferential boundaries secured together to form an anular cavity of variable cross section, aperture means venting said cavity to atmosphere, and air flow generating means mounted on said rigid annulus so as to induct air from the flexible annulus side of said bearing and discharge said air on the rigid annulus side.

2. A pendant air bearing adapted for operation in vertically suspended proximate relation with a ceiling surface comprising a lower rigid annulus and an upper flexible annulus having their respective circumferential boundaries secured together to form an annular cavity of variable cross section, aperture means in said rigid annulus venting said cavity to atmosphere, and air flow generating means mounted on said rigid annulus so as to induct air from the flexible annulus side of said bearing and discharge said air on the rigid annulus side.

3. A surface proximate air bearing comprising a rigid annular platform, an, annular flexible diaphragm disposed over the upper surface of said platform, means securing the outer margin of said diaphragm to the outer margin of said platform and the inner margin of said diaphragm to the inner margin of said platform, air flow generating means mounted on the lower surface of said platform in alignment with the opening in the latter defined by the inner margin thereof, said air flow generating means being operable to cause air flow through the opening in the platform in a vertical downward direction, and.

means providing communication between atmosphere and 4. In combination, with a substantially flat supporting surface, a surface proximate air bearing comprising a rigid annular platform, an annular flexible diaphragm disposed over the upper surface of said platform, means securing the outer margin of said diaphragm to the outer margin of said platform and the inner margin of said diaphragm to the inner margin of said platform, air flow generating means mounted on the lower surface of said platform in alignment with the opening in the latter defined by the inner margin thereof, said air flow generating. means being operable to cause air flow through the opening in.

the platform in a vertical downward direction, means providing communication between atmosphere and the annular cavity defined by the platform and diaphragm, a. motor operated load elevating device connected at its upper end to said platform in alignment with the geometric center of the latter, and a sling supported platform connected to the lower end of said elevating device.

5. In combination with a horizontal substantially flat supporting surface, a pendant air bearing comprising a rigid annulus and a flexible annulus having their respective circumferential boundaries secured together to form an annular cavity of variable cross section, means formed in said rigid annulus venting said cavity to atmosphere, air flow generating means mounted on said rigid annulus so as to induct air from the flexible annulus side of said hearing and discharge said air on the rigid annulus side, said air bearing being disposed adjacent said supporting surface with the flexible annulus side facing said surface, whereby upon operation of said air flow generating means and said supporting surface thereby establishing a pressure differential which maintains the air bearing in frictionless pendant relation with the supporting surface, said pressure differential further acting through said venting means in said rigid annulus to inflate said annular cavity and distend said flexible annulus upwardly so that a variable generally frusto-conical subatmospheric plenum chamber is formed between the flexible annulus and the supporting surface.

6. In combination with a horizontal substantially fiat supporting surface, a pendant air bearing comprising a rigid annulus and a flexible annulus having their respective circumferential inner and outer boundaries secured together to form an annular cavity of variable cross section, means formed in said rigid annulus venting said cavity to atmosphere, air flow generating means mounted on said rigid annulus in alignment with the opening formed by the inner boundary of said rigid annulus so as to induct air from the flexible annulus side of said bearing and discharge said air on the rigid annulus side, said air bearing being disposed horizontally and adjacent said supporting surface with the flexible annulus side facing said surface, whereby upon operation of said air flow generating means a partial vacuum is induced between said flexible annulus and said supporting surface thereby establishing a pressure differential which maintains the air bearing in frictionless pendant relation with the supporting surface, said pressure differential further acting through said venting means in said rigid annulus to inflate said annular cavity and distend said flexible annulus upwardly so that a variable generally frusto-conical subat'mospheric plenum chamher is formed between the flexible annulus and the supporting surface.

7. In combination with a horizontal substantially flat supporting surface, a pendant air bearing comprising a lower rigid annulus and an upper flexible annulus having their respective inner and outer circumferential boundaries secured together to form an annular cavity of variable volume, aperture means in said rigid annulus venting said cavity to atmosphere, a blower mounted on said rigid annulus so as to induct air from the flexible annulus side of said bearing and discharge said air on the rigid annulus side, said air bearing being disposed adjacent said supporting surface with the flexible annulus side facing said surface, whereby upon operation of said blower a partial vacuum is induced between said flexible annulus and said supporting surface thereby establishing a pressure differential which maintains the air bearing in frictionless pendant relation with the supporting surface, said pressure differential further acting through said venting means in said rigid annulus to inflate said annular cavity and bulge said flexible annulus upwardly to form a circumference of maximum upward distention lying closely proximate relative to said supporting surface, which circumference forms with said surface a horizontal air flow restricting gap of circular plan so that a. variable cross sectional generally frusto-conical subatmospheric plenum chamber is formed between the flexible annulus and the supporting surface.

8. The structure set forth in claim 5 wherein the supporting surface is provided with a pair of parking channels having inturned flanges adapted to support said bearing when said blower is inoperative.

References Cited in the file of this patent UNITED STATES PATENTS 1,698,482 Nicin Jan. 8, 1929 2,942,736 Landsiedle et al June 28, 1960 3,055,613 Taylor Sept. 25, 1962 

1. A SURFACE PROXIMATE AIR BEARING COMPRISING A RIGID ANNULUS AND A FLEXIBLE ANNULUS HAVING THEIR RESPECTIVE CIRCUMFERENTIAL BOUNDARIES SECURED TOGETHER TO FORM AN ANULAR CAVITY OF VARIABLE CROSS SECTION, APERTURE MEANS VENTING SAID CAVITY TO ATMOSPHERE, AND AIR FLOW GENERATING MEANS MOUNTED ON SAID RIGID ANNULUS SO AS TO INDUCT AIR FROM THE FLEXIBLE ANNULUS SIDE OF SAID BEARING AND DISCHARGE SAID AIR ON THE RIGID ANNULUS SIDE. 